1. Technical Field
The present disclosure relates to a mold for insert molding. More particularly, the present disclosure relates to a molding device and process having components to accommodate size variation of an insert while preventing flashes from escaping from the cavity at the insert location.
2. Background
Insert molding by an injection molding method has been widely used in the prior art, which an insert component is covered with resinous material in conformity with the contour of the former. Generally, in the injection molding method, an insert component is located and fixed at a predetermined position within a cavity of a mold made, for example, of metal and is clamped in this state. Then, molten resin injected from a nozzle of a molding machine is filled in the cavity via a sprue, a runner and a gate to cover the outer circumference of the insert component in conformity with the cavity-forming surface, thus forming the insert-mold product.
In producing plastic parts having metal inserts such as a member of an end effector assembly, a very tight fit of the insert in the cavity is desired so that flash (excess plastic) cannot escape. Flash around the insert is cosmetically undesirable, and the flash may also interfere with subsequent assembly operations involving the part. One solution is to allow the flash to be produced, but to then remove that flash in a subsequent operation. However, labor costs involved in removing the flash are proportionately exorbitant. The best solution is to avoid the production of the flash during the process. In the prior art, the most common method of avoiding the production of flash has been to machine the insert opening in the cavity to very close tolerances (e.g., plus or minus 0.001 inch). Even so, flash frequently escapes due to the ordinary production tolerances found in the inserts themselves. Additionally, such molds can be expensive to manufacture. Moreover, variations in insert sizes may cause manufacturing defects. For example, if an insert is too small, flashes occur at shutoff. If an insert is too large, the clamp pressure of the tool may crush the insert and/or damage the mold tool.